A fluid handling tube often is used to store and manipulate fluids in laboratory settings. A fluid handling tube sometimes is configured for placement in a chamber of a centrifuge for centrifugation, and can be referred to as a centrifuge tube or a micro-centrifuge tube. A fluid handling tube often includes a tube body and a cap that can be engaged with the tube body. The cap that can be engaged with the tube body to protect fluid in the tube from spillage, evaporation and/or contamination, for example. A cap can be in sealing engagement with a tube body, and a portion of such a cap can be inserted into the tube body interior to facilitate an air-tight seal.